Acoustic insulating vehicle component

ABSTRACT

A vehicle component has a vehicle body part in combination with an acoustic insulating structure which interacts therewith. The acoustic insulating structure has an outer covering having a shield. The shield is spaced at a distance from the vehicle body part by an intermediate layer. In a particular embodiment, the intermediate layer is at least partially filed with a foam layer which is pressed against the body part by the shield. The shield is preferably perforated and the foam layer is protected against humidity and moisture by a thin plastic film. The outer covering can be conventionally fastened to the underside of the body part.

FIELD OF THE INVENTION

The present invention concerns a vehicle component according to thepreamble of claim 1 and an external cover for this.

DESCRIPTION OF THE RELATED ART

It is known to equip the floor panel of a vehicle with an acousticallyactive i.e. sound-insulating and/or sound-absorbing interior lining.Usually such a lining has a sound-insulating damping layer which is laidor glued directly onto the floor plate. In vehicles of higher comfort,on this vibration-damping and sound-insulating layer is applied afurther sound-absorbing foam or fibre fleece layer and a heavy airtightcarpet layer. These additional layers are matched to each otheracoustically so that they can interact with each other as an acousticspring-mass system. It is also known to apply a protective coating tothe outside of the floor panel. This protective coating protects thefloor panel mechanically and/or chemically for example against stonechips or road salt. Naturally this protective coating, referred to belowas the underfloor coating, also contributes to additional damping of thevibrations of the floor panel.

As underfloor protect-on usually a relatively expensive PVC coating ofapproximately 1 mm thickness is sprayed on. Such a layer leads to aweight increase of around 1-1.5 kg/m² and undesirably releases largequantities of chlorine on recycling.

SUMMARY OF THE INVENTION

It has been found that the multiplicity of layers and coatings ofdifferent functions applied to the floor plate undesirably increase thetotal weight of the vehicle and undesirably reduce the passenger space,in particular the foot space. The general aim of the modern vehicleindustry however is to make vehicles lighter, more spacious and moreeconomic.

It is therefore the task of the present invention to create a vehiclecomponent which allows the foot space of the vehicle to be structuredmore spaciously without loss of acoustic effectiveness.

In addition a vehicle component is created which in comparison withconventional vehicle floor configurations is lighter and more costeffective and in particular raises no special disposal problems.

This task is solved according to the invention with the vehiclecomponent according to claim 1 and an outer covering according to claim13, and in particular in that on the outside of the body part is applieda strengthening shield at a distance from the said part which togetherwith the body part forms a double floor structure. This double floorstructure has a sound-insulating effect and can be combined with furthersound-insulating and/or sound-absorbing elements.

In a preferred development of the vehicle component according to theinvention a foam layer, in particular a soft foam, is introduced in thecavity of the double floor where the foam, preferably on its side facingthe body part, is fitted with a profile. Such profiled dissipativelyacting layers are known for example from EP 0 474 593 (which is herebyincluded in full scope as a constituent of this application) and restloosely against the body part and damp the body vibrations. For this thesoft foam and double floor are dimensioned such that the profiled softfoam is pressed against the body part by the shield of the double floor.

In a further preferred design of the vehicle component according to theinvention the double floor is combined with an ultralight absorptionpackage of the known type (for example according to WO98/18657, thecontent of which forms part of this application). Instead of a heavylayer this has a microporous stiffening layer. In this embodiment boththe sound-insulating bituminous damping layer inside the vehicle and theheavy layer of the spring-mass system of the interior lining can beomitted.

This creates an acoustically active vehicle component which isconsiderably lighter than conventional systems and in the interior ofthe vehicle has a lower thickness. It is evident that by suitablecombination of the double floor according to the invention withsound-insulating and/or sound-absorbing systems,of the known type, theacoustic efficacy can be improved further.

Preferred developments are defined by the features of the sub-claims.

The invention is now explained in more detail below with reference todesign examples and the figures. Here:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagrammatic view of a conventional vehicle floor;

FIG. 2 shows a diagrammatic view of the vehicle component according tothe invention;

FIG. 2a shows an enlarged view of a portion of the vehicle component ofFIG. 2.

FIG. 3 is a diagrammatic view of a further development of a vehiclecomponent according to the invention;

FIG. 4 is a diagram of the acoustic efficacy of the various vehiclecomponents with different equipment.

DETAILED DESCRIPTION

The vehicle floor 1 shown in FIG. 1 has a conventional structure. On theinside of the floor plate 2, for example a steel plate approximately 0.8mm thick, is applied a bituminous damping layer 3. This damping layer 3usually weighs around 2.3 kg/m² and is glued in place. On this dampinglayer 3, depending on vehicle equipment level, is applied a more or lessheavy sound-absorbing spring-mass system 4, the spring layer 5 of whichconsists of a fibre fleece approximately 20 mm thick, an open-pore foamor a foam flock fleece (KFF), the mass layer 6 of which consists of aheavy layer (EPDM) weighing approximately 3.2 kg/m² or a correspondingdecor or carpet layer. On the outside 8 the floor plate 2 has anunderfloor coating 7 approximately 1 mm thick which usually consists ofsprayed on PVC. The total weight of the acoustically active structureapplied to such a vehicle floor 1 is therefore at least 8.0 kg/m².

In contrast FIG. 2 shows a vehicle component 10 equipped according tothe invention. In its simplest embodiment this has a shield 11 at adistance from the outside 8 of the floor plate 2 and together with thefloor plate 2 forms a double floor 13. The cavity between the floorplate 2 and the shield 11 in this simple embodiment has a thickness of afew millimetres, in particular 5 to 15 mm, and is filled only with air.In a preferred embodiment this cavity is filled with a sound-insulatingand/or sound-absorbing intermediate layer 12. Suitable materials forthis intermediate layer are open-pored and known to the expert for sometime. In order to clamp the shield 11 to the body part 2, suitable means17 are provided. These means can comprise any conventional connectiontechnology known today for example bolting, clipping etc. and inparticular can use the weld bolts normally used in vehicles. The bodypart 2 consists of a conventional body panel for example made of a 0.8mm thick steel plate whereas the shield 11, in a preferred embodiment,consists of a fibre-and/or filler-reinforced plastic 0.5 mm to 3.0 mmthick, preferably 1.0 mm to 2.4 mm thick, with a basis weight of around3 kg/M².

The double floor arrangement according to the invention, because of thespring effect of the air, leads to improved sound insulation outside thesandwich resonance of the spring-mass structure.

Suitable materials for structuring the shield 11 according to theinvention are shown in the table below:

E-modulus of Fibre Filler bending in in w. % Fibre Type Matrix GroupDensity GPa GMT 20 Glass PP Thermoplastic 1.03 2.9 LFT 20 Glass PPThermoplastic 1.03 2.9 LFI 20-25 Glass PUR Thermoset  0.5-1.15 2.0-5.5NMT 30 Green flax PP Thermoset 1.02-1.03 3.5 R-RIM 20 Glass PURThermoset 1.2 1.2 Injection 20 Glass PP Thermoplastic 1.04 3.8 mouldingSMC 25 Glass UP resin Thermoset 1.7-2.0 8.5-14

The particularly advantageous feature of these materials is their highrigidity and low density. Further density reductions can be achieved viaother additional fillers e.g. by means of hollow glass balls with aparticle size of 10 to 200 μm and an effective density of 0.14 to 0.70g/cm³. Suitable fibre fillers are aramite, carbon, hybrid, textile,glass, natural, polyamide, polyester or mineral fibres.

In a preferred embodiment the shield 11 has perforations i.e. at least apartial hole structure. These perforations can have a diameter of 0.5 mmto 3 mm, preferably 1.0 mm, and are for example arranged at intervals ofapproximately 2.5 mm from each other. In order to protect the open-poreintermediate layer 12 from moisture and humidity, advantageously atleast between shield 11 and intermediate layer 12 is applied a thinplastic film. On the outside of shield 12 can be applied an open-porefibre or carpet layer to achieve additional protection against stonechips and/or water. Such a fibre and/or carpet layer also improves theair flow behaviour on the outside of shield 11 (shark-skin principle).Such a double floor is particularly suitable for the outer covering ofwheel arches. The acoustic efficacy of the double floor according to theinvention is particularly useful in this application.

In a further development of the double floor arrangement according tothe invention on the inside 9 of the body part 2 is provided aconventionally constructed sound-insulating spring-mass system 14. Inthis embodiment this comprises a sound-dissipating porous layer ofreduced thickness acting as a spring (soft light foam, heavy foam orfibre fleece layer) and a slight heavy layer 6 acting as a mass. Or onthe inside 9 of body part 2 is provided a sound-insulating andsound-absorbing spring-mass system 14 similar to the system described inWO98/18657, consisting of a porous layer 14 acting as a spring and amicroporous cover layer 16 acting as a light mass.

In a further development of the double floor arrangement according tothe invention, on the inside 9 of body part 2 is provided aconventionally constructed sound-absorbing spring-mass system 14. Inthis embodiment this comprises an absorber layer 15 (light foam layer)acting as a spring and a porous cover or heavy layer 16 acting as a masslayer. The double floor arrangement according to the invention thusallows the omission of the damper layer 3 and underfloor coating 7conventionally applied. This allows the weight of the acousticallyactive structure to be reduced substantially. In particular, thesound-insulating damping layer 3 can be dispensed with the interiorlining 14, and the protective coating 7 can be dispensed with the outerlayer 13. This leads to a weight saving of more than 2 kg/m² withoutrestricting the acoustic effect as corresponding comparison measurementsconfirm. At the same time the thickness of the interior structure 14 canbe reduced.

In a preferred development of the vehicle component according to theinvention as shown in FIG. 3, the intermediate layer 12 consists of anelastic PU foam 19. This foam 19 has a profile which lies on the outside8 of body part 2 and in particular is pressed by shield 11 onto thisbody part 2. This provokes a vibration damping of the body part 2. Theprofiling of this foam 19 leads to the formation of a labyrinth-like airlayer 18 between the body part 2 and the foam layer 19, which air layer18 also has a dissipative effect in interaction with the vibrating bodypart 2. Evidently this foam layer 19 can be used to make contact bothover the full area and also partially. In a particular embodiment thecavity between the shield 11 and the body part 2 is filled onlypartially with an intermediate layer 12. In addition the inside 9 of thebody part 2 can also be partially covered with a damping layer 3.

In further developments of the construction according to the invention,instead of a conventional spring-mass system 14 an ultralight absorptionpackage is used. Such absorption packages are for example described inWO98/18657 and instead of a heavy layer 6, 16 have a microporousstiffening layer which has a total air flow resistance of 500Nsm⁻³<R_(t)<2500 Nsm⁻³ and a surface mass of 0.5 kg/m²<m_(F)<1.6 kg/m².The bending strength of such a microporous stiffening layer is 0.005Nm<B<10.5 Nm.

The diagram in FIG. 4 shows the acoustic efficacy of the various vehiclecomponents. Curve 22 shows the acoustic behaviour of a conventionalstructure according to FIG. 1.

The development of this curve 22 in the area of 200 Hz shows acharacteristic insulation minimum and clearly shows that with thissound-damping structure the sound insulation efficacy runs essentiallylinear at higher frequencies and at approximately 10,000 Hz has a valueof around 80 dB. This development corresponds rather precisely to theacoustic behaviour of the double floor according to the invention incombination with a classic spring-mass system. In contrast curve 21shows the sound insulation behaviour of the sound-absorbing ultralightinsulation system cited above (according to WO98/18657) on aconventional floor plate equipped with underfloor protection and dampingcoating. Here the sound insulation efficacy R has no resonance loss andshows an improvement in comparison with the configuration in curve 22 ofup to 10 dB in the area of around 200 Hz. The insulation efficacy R ofthe configuration according to curve 21 rises above 500 Hz almost linearwith the—logarithmic—frequency and with a slightly lesser gradient. Theacoustic behaviour of a preferred design form according to the inventionis indicated by curve 23. In this embodiment the double floor accordingto the inversion is combined with the ultralight insulation systemaccording to WO95/18657.

The benefits of the vehicle component according to the invention areimmediately evident to the expert. In particular with the vehiclecomponent according to the invention the heavy vibration-damping layersare replaced by stiffening and sound-absorbing layers. The reduction inlayer thickness in the area of this vehicle foot room achieved by thevehicle component according to the invention proves particularlyadvantageous. It is evident that by omission of the heavyvibration-damping layers, the arrangement according to the invention ismore economic than conventional insulation systems. The external noisereduction in the wheel arches because of the improved sound insulationeffect has proved particularly advantageous. At the same time thepresent arrangement gives improved corrosion protection and with thisarrangement a lower CW value can be achieved if the double floorarrangement is fitted with a surface structure (carpet or golf ballstructure) on the outside. Further developments of the double floorarrangement according to the invention and suitable combinations withother acoustically active systems of known types lie within the scope ofthe knowledge of a person skilled in the art and are not explained inmore detail here. It is evident that the double floor arrangementaccording to the invention can be used not only on vehicle floors or inwheel arches but equally well for engine encapsulation.

What is claimed is:
 1. Vehicle component comprising a body part incombination with an acoustically active structure, where theacoustically active structure has an outer cover which comprises ashield spaced from the body part by an intermediate layer, wherein theshield has a bending elasticity modulus of 1 to 15 Gpa and a densityfrom 0.3 to 2.5 g/cm³.
 2. Vehicle component according to claim 1,wherein the shield comprises a beaded panel, a fibre-reinforcedthermoplastic or a fibre-reinforced thermoset.
 3. Vehicle componentaccording to claim 2, wherein the intermediate layer comprises a foamlayer which lies at least partially on the body part.
 4. Vehiclecomponent according to claim 3, wherein the foam layer has at leastpartially a surface structure which lies on the body part.
 5. Vehiclecomponent according to claim 1, wherein the shield is at least partiallyperforated.
 6. Vehicle component according to claim 1, wherein betweenthe shield and the intermediate layer is arranged a water-impermeablefilm.
 7. Vehicle component according to claim 1, wherein the foam layerhas a water-impermeable sleeve.
 8. Vehicle component according to claim1, wherein the body part has an acoustically active interior lining. 9.Vehicle component according to claim 8, wherein the interior lining hasa spring-mass system.
 10. Vehicle component according to claim 8,wherein the interior lining has an ultralight absorption/insulationstructure with a microporous stiffening layer.
 11. Vehicle componentaccording to claim 1, wherein the body part is fitted on the inside atleast partially with a damping layer.
 12. An acoustically activestructure comprising an outer cover with a shield and an intermediatelayer, wherein the shield has a bending elasticity modulus of 1 to 15GPa and a density from 0.3 to 2.5 g/cm³.
 13. Outer cover according toclaim 12, wherein the shield comprises a beaded plate, afibre-reinforced thermoplastic or a fibre-reinforced thermoset. 14.Outer cover according to claim 13, wherein the shield has on a sidefacing a body part a foam layer which can lie at least partially on-thebody part.
 15. Outer cover according to claim 14, wherein the foam layerhas at least partially a surface structure which lies on the body part.16. Outer cover according to claim 12, wherein the shield is at leastpartially perforated.
 17. Outer cover according to claim 12, whereinbetween the shield and the foam layer is arranged a water-impermeablefilm.
 18. Outer cover according to claim 12, wherein the foam layer hasa water-impermeable sleeve.
 19. Vehicle component according to claim 1wherein said shield has a bending elasticity modulus of 1 to 6 Gpa. 20.Outer cover according to claim 12 wherein said shield has a bendingelasticity modulus of 1 to 6 Gpa.